[gryn]

don't conflate 'Objects' with 'Object Oriented Design', if you split your data Structures from you algos then your just using an OOP-language to do programming not doing OOP.

strong typing has nothing to do with OOP. static variable are replaced by singletons and other similar in spirit objects.

OOP today is a 'No true Scotsman' concept much like communism, agile, and other vague by design terms. You can't argue against it because every individual has at least one definition in his head and it shifts through the conversation toward the one that's not refuted by the claims.

the intent of such concepts is to hit you in the feels and trigger some ideals inside you, so that you associate the positive feelings you have toward those ideals to the concept.

if you argue about it as it is used in practice you will inevitably have someone bring up that java style OOP is not true OOP and that you should look intro Smalltalk or some other language that implement "Real OOP".

since arguing about specifics is a losing battle, lets argue about the bigger picture, if we take the goals of alain kay like he talked about in many of his talks his goals was to make systems more like biogology, but as a system designer the last thing you want to do is that. we don't know much about biology, people in that field a still reverse engineering pre-existing designs to this day and not designing much of their own from scratch. If you design a system you want to have the most control and foresight in the dynamics of your systems, uncontrolled & unintended emergent effects are your source of problems.

entangling data and behavior make your conceptual design state-space size explode, when you go full OOP you become an ontologist philosophizing about what is an X and what is an X-manager, X-Provider, ... and less of a system designer trying to make sure your system does not land in the wrong states.

[DrScientist]

Aren't you then just attacking a programming style that nobody actually uses or advocates?

One of the most influential books about OOP - "Design Patterns: Elements of Reusable Object-Oriented Software" - talks about composition, separating interface from implementation etc - not about hierarchies ( other than to prefer composition ).

[adrian_b]

Composition and "separating interface from implementation" are not specific to OOP languages.

Composition has been used since LISP I and ALGOL 60 in almost all programming languages.

"Separating interface from implementation" is also the main feature of the programming languages based on abstract types, starting with Alphard and CLU, which are not OOP languages and which predate the time when Smalltalk has become known to the public, launching the OOP fashion.

An abstract type is defined by an interface, i.e. by a set of functions that have arguments of that type and this is a programming language feature that is completely independent of the OOP features like member functions, virtual functions and inheritance.

All OOP languages have some kind of abstract types, though with a different point of view on the relationships between individual objects and types a.k.a. classes and the functions that operate on them, but there have been many languages with abstract data types without the OOP features.

Moreover "separating interface from implementation" has also been the main feature of all programming languages based on modules, starting with Mesa, Modula and Ada.

The features that identify an OOP language are the idea that the functions belong to individual objects, not to types, hence the member functions, the substitution of the union types (of the right kind, like in Algol 68, not of the pathetic kinds encountered in Pascal and C and derived languages) with virtual functions (to provide an alternative form of dynamic polymorphism, which is preferable for closed-source software, by allowing changes without recompilation, unlike with tagged unions where there are select/case/switch statements that must be recompiled when the union is extended), and the inheritance in a class hierarchy.

There are many languages that are multi-paradigm, like C++ or D, where you can choose whether to write a program in an OOP style or in a totally different style, but there are also languages where it is difficult to avoid using the OOP features, or even impossible, because all the available data types may be derived from some base "object" type, inheriting its properties.

[mcguire]

Much of the Design Patterns phenomenon involves convincing Java to do things that are idiomatic in other languages.